Having power problems while running track speeds...

[NorCal_250R]

So I have been here for awhile, and as many may know or not...I race AFM with the boys (and girls) there.

I have a 2008 250R.

So I have been experiencing some major problems I can't seem to diagnose lately.

I just got back from a 2 day intermediate school with Keigwin@theTrack...it was great...but...
Monday it was 103 degrees...and Tueday 100...

When my bike got hot, especially during the mid to late day the bike was running TERRIBLE! No power in the mid range (8-9.5K) and not much better on the top end...bike seems to vibrate much harder in the clipons and the foot pegs and had noticable power loss...not enough to stall or anything but where I decided to bring it in...

Had the same problem at the last race, where by mid race the bike was piping hot but had noticable lack of punch...

I have a the Factory Pro Jet kit (92 mains, switched to 96 mains didn't seem to help any...), Yoshimura Full exhaust, and Sportisi Ait Filter...

I thought it might be the BRT CDI, but I switched back to the stock CDI and as soon as the bike got really hot out there...same problem came back...

Any suggestions on what to look for?

Bike has about 5 race weekends and 4 trackdays on it...

[almost40]

is the bike overheating?? do you have a temp gauge installed?? My first thought is that your way too lean on the fuel and or your mixture screws need adjusting. did you sync up the carbs?? have you checked the plugs?? is the cooling fan working??

lets start with those questions anyway. the more info you can give the better.

[Alex]

I think you're bike's just trying to tell you that running Thunderhill when it's over 100 degrees out is generally a bad idea all around.

Kidding. Sort of.

Hope you can sort out its issues...

[RaceBikeRentals]

Do you still have the fan installed? I've run in 110 degree temps without fan and thermostat, and it was running very hot - around 265 degrees. Bike ran fine, though.

92 jets seem really, really lean. You rejetted to 96 and it made no difference? Have you checked your spark plugs to see if they're fried?

[NorCal_250R]

I don't have the bike...it's at my dad's. But I will get it back today and do the usuall tear down and check what was suggested...

I do not have a temp gauge...how do I install one, that would be great...

Factory Pro had told me to install 90 Mains...so the 92.5 seemed more than enough...but I had only time yesterday to put one 96 Main in...(thank you Matt Grey for being there with what I needed...)but that I guess doesn't mean much...I will check the plugs and go from there...

My dad had 92.5 in his and my bro-in-law had 95s and didn't seem to have the problem...but I know each bike is unique...

The carbs have never been sync'd and the mixture screws were set at 2.5 turns when I jetted it...needles at middle clip...

So I will start with plugs I guess and report back from there...

BTW...the headers seemed really blue on the top...which I know means lean...but one guy told me there that as air gets hot there is less of it, so he ususally steps DOWN a main, so I was even more confused...misinformation?

[kkim]

Originally Posted by NorCal_250R

one guy told me there that as air gets hot there is less of it, so he ususally steps DOWN a main, so I was even more confused...misinformation?

that is true when the jetting is spot on to begin with. From what I've seen, 92s as mains are really lean compared to what have been used by other people that have rejetted.

checking the plugs would tell you a lot.

[NorCal_250R]

So I might go to the 96 mains and see what happens...

[kkim]

yes, at least 2 of the same jets would be preferred.

have you made any changes to the intake/exhaust? Usually the 98s that come stock work well after the engines have been "opened up" a bit with intake and exhaust changes.

be sure to check your plugs to get a glimpse of engine health at this point. can't say what possible damage occurred when the bike was running "funny", but reading the plugs will.

[NorCal_250R]

I didn't get to open up the bike today...but I bought some new plugs...figured if I pull the old ones out, might as well drop new ones in...

How often to the racers on this board change their plugs out?
I'll still report the plug findings tomorrow when I pull them...pics too if I need to...

[ztrack157]

Most guys change them rarely Jordan.

[esi7esi7]

Here is some advice I was given when asking about jetting and elevation changes on the CMRA forum..

For the 08-10 Ninjas we have had to change jetting for temperature changes but not for elevation since the difference isn't enough to matter.

If you have an OEM airbox and a factory pro stage 1 kit we found a 90 main to work well when very hot and 92 main when cooler.

If you have pod filters and a factory pro stage 3 kit we found a 108 main works well when hot and 110 mains when it is a bit cooler. We tried 105s when it was super hot out but it was a bit lean in the midrange.

All engines are a bit different so it would be best to dyno your bike and read the ehxaust gases....or do a plug chop and pull the spark plugs. Either will tell you what you need to know.

Dean

[kkim]

Originally Posted by ztrack157

Most guys change them rarely Jordan.

change them, rarely, but read them? often, if they are having running problems, I'd say.

[ztrack157]

Originally Posted by esi7esi7

Here is some advice I was given when asking about jetting and elevation changes on the CMRA forum..

Thats Dean Thimjon he is my CMRA guy and hes a wizard with his understanding of the 250's. Hands down knows more about these new gen bikes than anyone.

[NorCal_250R]

So the plugs looked okay. But it appears I should have stuck with my 90 mains or 92s. I will run the bike with the 96s and just see what happens. I am thinking maybe the voltage regulator is getting really hot and maybe not working as well as it should. Any ideas?
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